A video course for high school teachers and college level instruction; 13 half-hour video programs, online text, professional development guide, and Web site; graduate credit available

The Habitable Planet: A Systems Approach to Environmental Science is a course for high school teachers and undergraduate students in environmental science. The content course will help teachers of biology, chemistry, and Earth science to provide more content in their classes. The course components include 13 half-hour video programs, a coordinated Web site which includes the streamed video programs, the course text online, five interactive simulations, background on the scientists who created the content and those whose research is documented, a professional development guide (also available in print form), and additional resources. Graduate credit is available for the course through Colorado State University.

This course begins with an overview of the Earth's systems — geophysical, atmospheric, oceanic, and ecosystems — as they exist independently of human influence. Following this introduction, the course explores the effect that human activities have on the different natural systems. Topics include human population growth and resource use, increasing competition for fresh water, and climate change. Each of the 13 programs features two case studies following top scientists in the field.

Harvard Smithsonian Center for Astrophysics in association with the Harvard University Center for the Environment. 2007.

1. Many Planets, One Earth
The early Earth was a much different planet than the one we know today. Ancient rocks provide evidence of the emergence of oxygen in the atmosphere and of a frozen Snowball Earth. Scientists Paul Hoffman and Andrew Knoll look at these clues to help explain the rise of complex animal life. Go to this unit.

2. Atmosphere
The atmosphere is what makes the Earth habitable. Heat-trapping gases allow ecosystems to flourish. While the NOAA Global Monitoring Project documents the fluctuations in greenhouse gases worldwide, MIT's Kerry Emanuel looks at the role of hurricanes in regulating global climate.
Go to this unit.

3. Oceans
Ocean systems operate on a range of scales, from massive systems such as El Niño that affects weather across the globe to tiny photosynthetic organisms near the ocean surface that take in large amounts of carbon dioxide. This program looks at how ocean systems regulate themselves and thus help maintain the planet's habitability. Go to this unit.

4. Ecosystems
Scientists from the Smithsonian Center for Tropical Research document the astounding abundance of diversity in tropical rainforests to discover why so many species coexist that are competing for the same resources. In North America, the Yellowstone Wolf Reintroduction project explores why removing just one species dramatically changed the distribution of plants and animals up and down the food web. Go to this unit.

5. Human Population Dynamics
The human population of our planet now exceeds 6.5 billion and is rising. Much of this growth is projected for the most environmentally fragile regions of the world. Will studying the history of the world's population growth help predict the Earth's "carrying capacity"? Go to this unit.

6. Risk, Exposure, and Health
We all require food, air, and water to survive  which are contaminated to some extent by man-made pollutants. Two studies, one in a rural western mining town and another in a dense urban population, reveal how these exposures impact health, and what can be done to reduce the risks. Go to this unit.

7. Agriculture
Will world population outrun food resources? The "Green Revolution" of the 20th century multiplied crop yields, in part through increasing inputs of pesticides and fertilizers. How can farmers reduce their use of agricultural chemicals and still produce enough food? Go to this unit.

8. Water Resources
While essential to the lives of humans and animals, fresh water only accounts for six percent of the world's water supply. Scientists in Florida's Everglades and the water challenged Southwest consider the optimum use of existing sources of fresh water for both humans and ecosystems. Go to this unit.

9. Biodiversity Decline
Species are being lost at a rapid rate in rainforests and coral reefs. Yet many species still have not been discovered. Tropical scientists struggle to keep ahead of the bulldozers as they work to understand this complex ecosystem. And an ocean biologist predicts the death of life and the "rise of slime" in the sea. How can we protect the biodiversity of these vulnerable ecosystems? Go to this unit.

10. Energy Challenges
Global energy use increases by the day. Polluting the atmosphere with ever more carbon dioxide is not a viable solution for our future energy needs. Can new technologies such as carbon sequestration and ethanol production help provide the energy we need without pushing the concentrations of CO2 to dangerous levels? Go to this unit.

11. Atmospheric Pollution
Once released, air pollutants react chemically with each other under solar radiation to become even more dangerous secondary pollutants. A company in the Northeast U.S. tracks the emission of pollutants at street level, while an international long-term study follows plumes of pollution from Mexico City across the continent and beyond. Go to this unit.

12. Earth's Changing Climate
Tropical glaciers are the world's thermometers; their melting is a signal that human activities are warming the planet. A California project tries to predict whether natural ecosystems will be able to absorb enough additional carbon dioxide from the atmosphere in the next 50 years to mitigate the full impact of human-induced greenhouse gas emissions. Go to this unit.

13. Looking Forward: Our Global Experiment
Earth's essential systems are being stressed in many ways. There are many tipping points in the environment, beyond which there could be serious consequences. Will human ingenuity, resiliency, and cooperation save us from the worst outcomes of our global experiment? Go to this unit.